I would say I tanked the boss and didn't die, which is true. But in regards to that, The party makeup was 2 c/r and 2 druid/wd. Both of us C/R tanked the boss as it's easy(habit) to use our aggro skills and pull the boss off one another. While I Held initial aggro and the aggro at the end, we traded tanking the boss back and forth with the other c/r dying a few times.
In that regard I will point out the boss never reset HP. I've seen the boss in past reset HP many times upon Tanks death. Nor did the other C/R die while he held majority aggro from the boss. Also this isn't first time i've seen more then one person tank boss during a fight. though it is first time with multiple tanks where one of the those tanking died during the fight. (previous one i've seen was a k/? not in party and in another guild who came in and started using all his skills while fight was ongoing and brought their own pocket healer).
As to despawn and reappearing it happened after boss died within 20 seconds. Vanished while the loot window was open and nothing had been taken. The Body reappeared still lootable allowing us to get the proofs of myths and runes off teh boss then became untargetable after looting staying the way picture in above post shows.